PUBLIC HEALTH ASSESSMENT
Select PCB Exposure Pathways
AGANA POWER PLANT
MONGMONG, GUAM
Built in 1949, the Agana Power Plant (APP) was owned and formerly operated by the U.S. Navy. The APP provided electricity not only to the Navy—particularly Naval Air Station (NAS) Agana—but also to the government of Guam and customers throughout the central and northern parts of the island.The 1995 closure of NAS Agana eliminated the Navy's need for the power plant. Consequently, the Navy Public Works Center and Guam Utilities Department, which formerly operated the plant, discontinued generating power. After the Navy discontinued its power generating activities, the Guam Power Authority (GPA) began using the power plant as a substation, and the plant continues to operate as such. Today, APP receives power from one or more power plants on the island and redistributes it to area residents, businesses, and municipalities.The Navy, however, still owns APP.
In the past, APP used polychlorinated biphenyls (PCBs) as cooling oils for its electrical transformers and switching-gears. By 1989, most transformers and related equipment were either removed or the oils replaced with non-PCB coolants. In 1998, as part of its standard turnover procedure for the transfer of former industrial properties, the Navy tested for traces of chemicals that could be harmful to humans and the environment. PCBs, dioxins, and polycyclic aromatic hydrocarbons (PAHs) were detected in soils and foods at or near APP. The Navy is currently characterizing and cleaning up the contaminated areas.
The Agency for Toxic Substances and Disease Registry (ATSDR) prepared this public health assessment to evaluate exposure pathway s and to respond to community concerns about past and current exposures to contaminants associated with the Agana Power Plant in Guam. ATSDR evaluated environmental information for all areas of contamination on and from the site and identified eight exposure pathways. This document reports on three of those pathways: 1) past and current exposures to PCBs and other contaminants from eating foods harvested in the Agana Swamp and River, 2) past and current exposures to PCBs from gardening and playing in the soil contaminated by runoff from the APP, and 3) past and current exposures to PCBs from swimming and wading in the Agana Swamp and River. ATSDR determined that none of the chemical exposures pose a public health hazard.
1) Eating Foods from the Agana Swamp and River
Eating foods from the Agana Swamp and River introduces two exposure situations: 1) people eating fish, eels, and snails harvested in the Agana Swamp and River, and 2) people eating fruits and vegetables grown in the Agana Swamp. PCBs and other chemicals have been found in fish, eels, and snails from the Agana Swamp. ATSDR evaluated the amount of people's exposure to PCBs, dioxins, and PAHs from eating fish, eels, and snails over many years. Based on a review of health-related information on these chemicals, ATSDR concludes that the PCB, dioxin, and PAH exposure from eating those foods is too low to result in harmful health effects, even to sensitive groups such as children.
However, bacterial contamination has been detected in Agana Swamp and reported in the Agana Springs since the 1960s. Thus, bacterial contamination of fish is possible. If people choose to eat the fish and other foods, thoroughly cooking it will help to reduce the hazards associated with bacterial contamination, including gastrointestinal problems. People should not eat aquatic snails unless they are thoroughly cooked to kill the parasites in them. Also, if one has open wounds and cuts, handling raw, infected fish might increase the risk of infection.
2) Gardening or Playing in the Soil from the Runoff Ditches
People could be exposed to PCBs and other contaminants in soils when playing in the dirt or drainage ditches, and when gardening—but the levels are too low to pose a public health hazard. For most people, PCBs enter their bodies primarily through the foods they eat. Thus, contact with contaminated soils is unlikely to be an important contributor to an individual's total body burden. In fact, studies of people living in the areas with PCB-contaminated soil have not demonstrated adverse health effects that could be attributed to PCBs from soil.
Relatively low levels of PCBs and other contaminants were found in soil samples from both the Agana Power Plant property and in runoff areas. The data and information reviewed does not indicate that large, highly concentrated spills of PCBs or other chemicals occurred. Therefore, in the past, PCBs and other chemicals in soil were also probably low.
3) Swimming and Wading in the Agana Swamp and River
Because PCBs do not easily dissolve in water and would in any event have been diluted by the large volume of water in the swamp, touching the water likely would not have posed a chemical health hazard. However, biological contamination in the swamp, from sources such as leaking septic tanks and sewage systems, is still possible. Therefore, people with open cuts or wounds who swim or wade might have an increased likelihood of infection. Eye and throat infections are also possible. And those who accidentally ingest the water could increase their risk of gastrointestinal problems such as diarrhea and abdominal cramps.
In the September 2000 Health Consultation, ATSDR outlined numerous possible sources of environmental pollution, with past and present activities where people could be exposed. These are the following:
Past and Present Activities discussed in this public health assessment
Past and Present Activitiesdiscussed in a second Public Health Assessment (PHA)
This public health assessment (PHA) primarily evaluates possible exposure situations associated with polychlorinated biphenyls (PCBs) from the Agana Power Plant (APP) in Guam. This document will address these three past and present activities:
Eating Foods from Agana Swamp or raised locally
Fish, Eels, and Snails
Fruits and VegetablesPlaying in the Dirt or Runoff Ditches and Gardening
Swimming and Wading in Agana Swamp and River
Remaining activities will be evaluated in future documents.
In addition, Mongmong residents reported five health conditions. This document provides information on these reported health conditions:
Appendix A describes the opportunities or conditions for exposure to occur (i.e., exposure situations), ATSDR's health conclusion category for the situation, and recommendations. ATSDR assigns conclusion categories to sites based on their public health hazard level. At APP, ATSDR has further clarified the "no apparent public health hazard" conclusion category by stating whether it is a current or past hazard. ATSDR's conclusion categories are explained in Appendix B.
Part of the Pacific Ocean's Micronesian Islands, Guam is the largest and most southern island of the Mariana Archipelago. The island has a total land mass of 212 square miles, excluding reef formations. Shaped like a footprint, Guam was formed by the union of two volcanoes. By airplane, this unincorporated U.S. territory is located about eight hours from Hawaii and three hours from Japan. Guam is west of the International Dateline and is one day ahead of the U.S. mainland (Official Web site of Guam 2002). In Apra Harbor the Port Authority of Guam services more than 1,000 vessels per year; it is the largest harbor in the Pacific between the Phillippines and Hawaii (Guam at a Glance 2002). Agana (Hagatna), the capital of Guam, is the center of civil government and much of the island's commercial activity.
A. Agana Power Plant and Surrounding Areas
The Agana Power Plant (APP) is a 3-acre property north of Roy T. Damian Road in the village of Mongmong. It is approximately ½ mile south of Agana Bay, about 2000 feet southwest of the southwest corner of NAS Agana, and 325 feet north of Agana Swamp (Figure 1) (US Navy 1999f). APP is surrounded by a chain-link-fence and comprises various buildings, switch yards, storage tanks, and cooling coils (US Navy 2001). The land surrounding the APP, including the APP West Drainage area and residential properties, is predominately privately owned. Land use is primarily residential, with the exception of unoccupied land north of the APP which contains remnants of an early U.S. Marine supply depot's building foundations (US Navy 1999f). Some people in this area eat locally raised cattle and pigs, foods from vegetable gardens, free-range chickens, and locally harvested land snails. (Note: This public health assessment will not address possible public health issues associated with eating locally raised foods other than from the Agana Swamp and River. A subsequent document will cover locally raised food issues.)
Mongmong is on the heights just south of the APP area and east of the Agana Swamp. The Agana Swamp lies along the drainage pathways from the Agana Power Plant, and portions of the Agana River upgradient of the APP (Figure 1). The Agana Swamp is a marsh associated with the Agana River. The marsh area nearest the APP, known as the "Utan" arm, is isolated from the rest of the marsh by a low upland ridge, on which is a residential neighborhood (US Navy 2000). The Agana Swamp and River area is largely undeveloped. It is mainly open space and woodland, with the exception of the taro root farm at the western portion of the Agana Swamp's "Utan" arm. Taro roots are harvested by farm workers and sold at local markets (US Navy 1999f). According to the villagers of Mongmong, for more than three generations they have fished, swam, and played in the Agana Swamp area. In addition, the area is used by homeless people for bathing and fishing.
B. Agana Power Plant Use and History of PCB Environmental Contamination
Built
in 1949, the Agana Power Plant was owned and formerly operated by the U.S. Navy.
The APP provided electricity not only to the Navy—particularly former Naval
Air Station (NAS) Agana—but also to the government of Guam and customers throughout
the central and northern parts of the island. The 1995 closure of NAS Agana
eliminated the Navy's need for the power plant. Nevertheless, after the Navy
discontinued its power generating activities, the Guam Power Authority (GPA)
began using the power plant as a substation, and the plant continues to operate
as such. Today, APP receives power from one or more power plants on the island
and redistributes it to area residents, businesses, and municipalities. The
Navy, however, still owns APP.
In the past, PCBs were used as coolant for the electrical transformers and switching gears at the plant. By 1989, most transformers and related equipment were either removed or the oils were replaced with non-PCB coolants (US Navy 1998b). In 1998, as part of the standard turnover procedure for the transfer of former industrial properties, the Navy tested for traces of chemicals that could be harmful to humans and the environment.
The Navy's testing suggested that rainwater from the plant might have carried PCBs into nearby neighborhoods and parts of the Agana Swamp by way of the drainage areas around the plant (US Navy 1998a). The Navy has discovered that PCBs entered several different media including fish, eels, and snails in Agana Swamp and soils along the drainage pathways near the power plant. According to the Navy's 1998 field sampling results, PCBs appear to have come from the leaks and spills of PCB coolant formerly used in electrical transformers and switches (US Navy 1999a). Also, at least one potential source area of PCBs in soil was identified inside the substation switch yards, POI-4. Other potential sources of PCB contamination are discussed in Section III.
The Navy is currently characterizing and cleaning up the contaminated areas. For detailed information on the Navy's continuing environmental investigation and remediation plans at the Agana Power Plant and surrounding areas, refer to APP's documents located at the three public repositories:
C. ATSDR Involvement at the Agana Power Plant
On January 14, 2000, Guam Environmental Protection Agency (GEPA) requested that ATSDR conduct a public health assessment to determine the possible public health impact of PCB contamination at the Agana Power Plant, and other contamination sources possibly impacting residents in the Mongmong community.
On February 29, 2000, the Department of the Navy, Pacific Division, Naval Facilities Engineering Command, requested ATSDR expedite the public health assessment because the community surrounding the Agana Power Plant had many health concerns.
On May 8-12, 2000, ATSDR conducted a site visit of the Agana Power Plant, Mongmong, Guam and began collecting information necessary to conduct the public health assessment. ATSDR reviewed available site-specific information and visually inspected plant and other areas where hazardous substances might have been released to the environment.
On May 9-10, 2000, ATSDR and Guam Department of Public Health and Social Services (GDPHSS) met with Mongmong residents to gather information about chemicals and human exposure—including PCBs—from the Agana Power Plant. The public availability sessions were held to give individuals and families an opportunity to talk privately with the public health representatives about their health concerns, problems or both.
In September 2000, ATSDR released a site summary consultation entitled Outlining Various Exposure Issues from Initial Site Visit- May 2000 to Mongmong and the Agana Power Plant, Mongmong, Guam. This document identified community health concerns and possible exposure issues. ATSDR concluded that no issues posed an immediate public health threat.
In January 2002, ATSDR released two fact sheets. The first, Community Questions and Answers on PCB Contamination and Health, was designed to give the people of Mongmong information about PCB contamination from the Agana Power Plant. The second, Update on ATSDR's Public for Agana Power Plant, Guam, was jointly released with GEPA and GDPHSS.
On February 24-March 1, 2002, ATSDR conducted another site visit of the Agana Power Plant. This visit featured a tour of the APP site and nearby sites in the Mongmong area. ATSDR representatives also met with the Congressman from Guam, the mayor of Mongmong, and representatives from the GEPA, GDPHSS, University of Guam (UOG), Water.
Environmental Research Institute of the Western Pacific (WERI), the U.S. Navy, and the Agana Restoration Advisory Board (RAB).
On March 1, 2002 ATSDR hosted a public meeting about the Agana Power Plant to update the community on the follow-up visit and to provide an opportunity to ask questions and express concerns related to the Agana Power Plant.
ATSDR examines demographic data (i.e., population information) to determine the number of people potentially exposed to environmental chemicals. This information is also used to determine the presence of sensitive populations, such as women of childbearing age (age 15-44), children (age 6 and younger), and the elderly (age 65 and older). Demographic data also provide details on population mobility which, in turn, helps ATSDR evaluate how long residents might have been exposed to environmental chemicals.
The population of Guam is estimated at approximately 155,000 persons (US Census Bureau 2002). This includes both island military and civilian populations. It also represents an increase of about 22,000 from the 1990 Census. The military personnel are largely concentrated in the northern portion of Guam, whereas the civilian population is mostly concentrated in Apra Harbor, Santa Rita, and villages in the coastal areas of Guam (US Navy 1996).
The majority of Guam's resident population, approximately 81,000 persons (52%), was born on Guam. The native Chamorrans are the largest ethnic group, comprising more than 42% of the island's population, including 5% who are Chamorran and another ethnic group. Of those not born on the island, a large number of Guam residents have emigrated from the Philippines, (21.1%), the United States Mainland (12.3%), and the Federated States of Micronesia (4.5%) (US Census Bureau 2002).
Toto and Maite are the closest communities to Mongmong. The Mongmong-Toto-Maite district has a population of about 5,800. In this district, at home 45% of the population speaks a language other than English: 27% speak Chamorro and 13.5% speak Philippine languages (US Census Bureau 2002).
E. Land Use and Natural Resource Use
The people of Guam use the land and natural resources in many ways. ATSDR examines these land and natural resource uses to determine activities that might put people at risk for exposure. This information is important because the types and frequencies of land use activities can affect exposure to contamination. ATSDR uses this information as part of the evaluation of contamination and exposure in this document. Below is some of the general information used in the analysis.
Fishing, and tourists from Japan, Taiwan, and Korea, are two of the island's natural resource uses (Official Web site of Guam 2002). Over the past 20 years the tourist industry has grown rapidly, creating a construction boom for new hotels and expanding older hotels. Other land use on Guam includes arable land (11%), permanent crops (11%), meadows and pastures (15%), forest and woodland (18%), and other (45%) (Official Website of Guam 2002). Four main sources of fresh water supply the island: groundwater, springs, the Fena Reservoir, and Ugum.
F. Quality Assurance and Quality Control
In preparing this PHA, ATSDR reviewed and evaluated information provided in the referenced documents. Documents prepared for the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and the Resource Conservation and Recovery Act (RCRA) programs must meet specific standards for adequate quality assurance and control measures for chain-of-custody procedures, laboratory procedures, and data reporting. The validity of the analyses and conclusions drawn in this PHA are determined by the availability and reliability of the referenced information. Based on our evaluation, ATSDR determined that the quality of environmental data available in APP site-related documents is adequate to make public health decisions discussed in this document.
EVALUATION OF ENVIRONMENTAL CONTAMINATION, EXPOSURE PATHWAYS, AND PUBLIC HEALTH IMPLICATIONS
To determine the presence of any associated past and current public health hazards, ATSDR reviewed the environmental data generated from both the U.S. Navy's reports and WERI investigations at APP and the Agana Swamp. From this review, ATSDR identified eight situations which have the potential for human exposure to PCBs and three of these situations are discussed in this document. These three exposure situations are discussed in the following sections. They are organized by the activities of people in certain areas that could result in exposure:
For each of these exposures, information will be provided on where the contamination was found, the extent of exposures as compared to other locations, and why ATSDR would or would not expect to find illness or disease.
PCBs, dioxins and polycyclic aromatic hydrocarbons (PAHs) have been detected in fish, eels, and snails in the Agana Swamp. ATSDR estimated the amount of PCB, dioxin, and PAH exposure from eating large amounts of fish, eels, and snails over many years. Using protective health guidelines, ATSDR believes that the PCB, dioxin, and PAH exposure from eating those foods is too low to result in harmful health effects, even to sensitive groups such as children.
However, a review
of information shows that the water and foods in the Agana Swamp and River could
possibly contain biologic contamination. Currently, this could pose a public
health hazard. The level of bacteria, viruses, parasites and other infectious
agents in water, fish, eels, aquatic (apple) snails, prawns, fresh water turtles,
and other foods—including fruits and vegetables—are not currently available.
But bacterial contamination has been detected in Agana Swamp and reported in
the Agana Springs since the 1960s. Therefore, bacterial contamination of fish
is possible. ATSDR has also observed leaks from septic tanks or sewage systems
entering the swamp. Thus, ATSDR that further characterization of this and other
hazards in the swamp is a prudent public health action. ATSDR also recommends
that the government of Guam consider a baseline evaluation of snails and other
organisms for biologic hazards as funding becomes available.
What Are the Possible Sources of Environmental Pollution in Agana Swamp?
During preliminary investigations, ATSDR reviewed extensive information to identify all possible sources of environmental pollution for the Agana Swamp, River and Springs (ATSDR 2000b). This helped to determine what contaminants could be in the foods. The following possible pollution sources are listed in the box below.
From this list it appears that a wide variety of activities that occurred in or near the Agana Swamp could have contributed to the contamination. The sampling done by the Navy in and near the Swamp would have picked up selected chemicals contamination currently being released from all sources at the locations sampled. At this point in time, ATSDR believes that there is no health hazard from the undisturbed (i.e., no construction or dredging activities) chemical contamination from these sources in the areas sampled. However, the potential for future release, especially during construction, dredging activities and storm events that disturb sediments, could be a future problem.
Where Did the APP Contamination Drain?
The Agana Swamp is a marsh situated along the drainage pathways from the Agana Power Plant and portions of the Agana River upgradient of the APP (Figure 2). The marsh area nearest the APP is known as the "Utan" arm, which is isolated from the rest of the marsh by a low upland ridge, on which a residential neighborhood is located (US Navy 1999f).
ATSDR reviewed the drainage areas from the Agana Power Plant to determine where PCB contamination from the plant could have moved. There are two main drainage areas: 1) the Outfall Drainage area (Upland and Wetland) and 2) the West Drainage area (Figure 2).
The drainage from the APP discharges at the Upland Outfall Drainage area and runoff flows through the area and down the hillside. Household refuse (e.g., tires, bottles, cans, and car batteries) was observed throughout this Tangantan scrub woodland area. Runoff flowing down the hillside appears to flow from the Upland Outfall Drainage area through the Wetland Outfall Drainage area and into the Agana Swamp. The Agana Swamp flows to the Agana River which eventually drains into the Agana Bay (US Navy 1999f).
Drainage from the west and southwest portions of the APP discharges into a partially lined swale-the West Drainage area—that runs parallel to Roy T. Damian Road, and eventually discharges into the Agana River near the Route 7A bridge. Because the swale conveys runoff from adjacent areas, APP might not be the only potential source of contamination in this area.
PCBs attach to soil particles and only move when water flow is strong enough to carry the soil particles. Therefore, drainage from the APP likely carried PCBs downgradient, along the drainage pathways. Navy testing results for APP and for the Agana Swamp PCBs found in swamp sediment were limited to the base of the Wetland Outfall Drainage area where drainage from the APP meets the Agana Swamp.
What Sampling Has Been Done to Confirm Where the Contaminants Are?
Soil, sediments, water, and a wide variety of foods in the Agana Swamp, the Agana River, and the Agana Bay have been sampled by different organizations. ATSDR reviewed sampling data from the U.S. Navy, WERI, and GEPA. Table 1 lists information about sampling conducted in the Agana Swamp, River, and Harbor (boat basin). The boat basin would only have slight mixing with Agana river water due to tides and currents moving across the reef. The Navy's sampling is the most comprehensive—it looked at most foods available in the swamp and screened them for several chemicals.
Table 1. Sampling Conducted in Agana Swamp, River, and Harbor
| Who Sampled | Media | What Was Sampled for | Location | Date |
| U.S. Navy | Fish, eels, snails, vegetables, and fruits | PCBs, dioxins, PAHs, volatile organic compounds, semi-volatile organic compounds | APP, Agana Swamp and River, drainage areas, residential property | 1998, 1999, 2000, 2001 |
| Sediment and soil | PCBs, dioxins, PAHs, volatile organic compounds, semi-volatile organic compounds, metals | |||
| University of Guam WERI* | Fish, shellfish, and sediment | PCBs | Agana Harbor | 1997, 1999 |
| University of Guam Marine Laboratory† | Snails | Parasites | Agana Swamp | 1999 |
| Guam EPA‡ | Water | Sewage | Agana Swamp | 2000 |
* Denton et al. 1997; Denton et al. 1999;
† B. Smith, Marine Laboratory, University of Guam, personal communication, 2000
‡ Notice of Violation 2000
Biologic Contamination in the Agana Swamp and River
The levels of bacteria,
viruses, parasites, and other infectious agents in water, fish, eels, aquatic
snails (i.e., apple snails), prawns, fresh water turtles, and other foods, including
fruits and vegetables, are not currently available. The Marine Laboratory at
the University of Guam detected meningoencephalitis-causing parasites in aquatic
snails from the Agana River and Swamp (B. Smith, Marine Laboratory, University
of Guam, personal communication, 2000). Still, according to Guam Public Health,
no cases in the last 20 years have been traced to eating snails or other foods
from the Agana Swamp (R. Haddock, Guam Public Health, personal communication,
2000). Cooking snails thoroughly will kill the parasites and reduce the risk
of illness. The USGS has also reported bacterial contamination in waters from
the Agana Springs, which is the source of water for the Agana River (Ward et
al 1965). In addition, ATSDR observed wastewater leaking from septic tanks and
sewage systems and entering the swamp. Progress and repairs have been made on
sewage treatment plants, but because of the age of the systems, future leaks
are possible. The initiatives to provide more modern septic systems including
hooking up homes to maintained sewer lines will help decrease the levels of
this contamination. Bacterial contamination from either of these sources could
lead to the contamination of food sources in the Agana Swamp and River. Foods
harvested in the Agana Swamp and River should be thoroughly cleaned and cooked
to kill all bacteria, viruses, parasites, and other infectious agents. ATSDR
recommends further characterization of biologic hazards in the swamp. ATSDR
also recommends that the government of Guam consider, as funding becomes available,
a baseline evaluation of snails and other organisms on Guam for micro-organisms.
Chemical Contamination in the Agana Swamp and River
The data collected by the U.S. Navy were used to conduct this health assessment for the chemical contamination of foods from the Agana River and Swamp. The sampling of biota in this area is available to make a health determination regarding chemical contaminants sampled in foods at specific locations.
Fish, Eels, and Snails
The Navy sampled several varieties of fish, eels, and snails from the Agana Swamp and River for various chemical contaminants, including PCBs, dioxins, and polycyclic aromatic hydrocarbon (PAHs).
Table 2 lists the fish, eels, and snails caught in the Agana Swamp and River and analyzed for PCBs. The U.S. Food and Drug Administration (FDA) has established tolerance levels for PCBs in fish and shellfish in interstate commerce. The FDA limits are used to determine whether or not the food is safe to consume over an extended period of time and requires total PCB levels in fish and other seafood for commercial distribution or consumption to be below 2 mg/kg. Of the four types of fish, eels, and snails listed in Table 2, the highest average value, tilapia, is 14 times below the FDA level.
Table 2. Total PCBs Sampled in Fish, Eels, and Snails in Agana Swamp and River*
| Apple Snails | Catfish fillet | Eel fillet | Tilapia fillet | |
| # Sampled | 18 | 12 | 9 | 1 |
| Average (mg/kg) | 0.0025 | 0.021 | 0.059 | 0.14† |
| Range (mg/kg) | ND to 0.0089 | ND to 0.049 | 0.013 to 0.16 | |
| FDA level (mg/kg) | 2 | 2 | 2 | 2 |
* Data from US Navy database provided to ATSDR April 2002;
† Not an average
Table 3 presents the concentrations of total dioxins (as 2,3,7,8-TCDD WHO-TEQ—see Appendix C for explanation) in fish, eels, and snails from the Agana Swamp and River. The FDA does not currently have a regulatory level for dioxins in fish for commercial distribution or consumption, but USEPA uses a 2.1E-8 mg/kg risk based concentration (RBC) for fish. Some of the dioxin levels in the fish, eels, and snails from Agana Swamp and River exceed this value. The USEPA's RBC is, however, determined using a series of health protective factors. And, as described later in the exposure evaluation section, the dioxin levels in these fish, eels, and snails are not likely to cause adverse health effects.
Table 3. Total Dioxins Sampled in Fish, Eels, and Snails in Agana Swamp and River*
| Apple Snails | Catfish fillet | Eel fillet | Tilapia fillet | |
| # Sampled | 3 | 4 | 2 | 1 |
| Average (mg/kg) | 3.60 x 10-8 | 3.38 x 10-7 | 1.05 x 10-6 | 3.91 x 10-7† |
| Range (mg/kg) | 3.14 x 10-9 to 9.57 x 10-8 | 6.46 x 10-8 to 3.74 x 10-7 | 8.58 x 10-7 to 1.23 x 10-6 | |
| EPA's RBC (mg/kg) | 2.1 x 10-8 | 2.1 x 10-8 | 2.1 x 10-8 | 2.1 x 10-8 |
* Data from US Navy database provided to ATSDR April 2002
† Not an average
Polycyclic aromatic hydrocarbons (PAHs) were also analyzed in the samples of fish, eels, and snails. The 16 most potent PAHs are evaluated based on their toxic equivalency factors (TEFs) relative to benzo(a)pyrene, the most toxic of the PAHs. The adjusted concentrations of PAHs were added together and evaluated as a total concentration. The concentrations were very low and none of the samples exceed the USEPA's health protective RBC.
Fruits and Vegetables
The Navy sampled taro, atis, breadfruit, calamansi lemon, coconut milk, and coconut meat for PCBs and one sample of taro for dioxins (US Navy 1999f). General studies have shown that fruits and vegetables do not readily take up highly chlorinated PCBs and, as might be expected, PCBs were not detected in any of the plant samples (ATSDR 2000c).
Total dioxins were measured in the one sample of taro root taken from the taro root farm in the Utan Arm of the Agana Swamp. The concentration was 0.0000013 mg/kg. As stated, dioxins can form from burning PCBs. But despite the fact that community members have reported fires in the Agana Swamp, burning of the low levels of PCBs found in the swamp should not have produced significant levels of dioxins. Although there was only one sample analyzed for dioxin, ATSDR concluded that dioxins are not a health hazard in taro root.
If people are interested in setting up farms, they should first contact the GEPA before they begin because there may be multiple pollution sources in the area. For additional information on setting up farms, people should contact the Guam Department of Agriculture.
Exposure Evaluation and Public Health Implications for Eating Fish, Eels, and Snails from the Agana Swamp and River
To relate chemical toxicity to the form of chemical exposure associated with eating contaminated fish, eels, and snails, the nature and extent of that exposure must be determined. To determine how likely people are to have adverse health effects from eating fish, eels, and snails, ATSDR performed screening-level mathematical calculations. These included exposure dose estimates and risk calculations incorporating a set of assumptions about exposure. In addition to calculations, ATSDR reviewed numerous references of the most current available scientific literature, including health studies, epidemiological studies, animal studies, occupational studies, and exposure investigations. The information used relates the environmental concentration (the level or amount of contaminant) to an exposure dose or an amount taken into a person's body. To obtain an exposure dose for the individuals exposed to contaminated fish, eels, or snails, several health protective assumptions were made about the exposure. These assumptions overestimated the amount of contaminants that people would ingest. Appendix D describes how ATSDR assesses exposure and Appendix E contains assumptions and methodology for calculating exposure doses.
PCBs - Fish, Eels, and Snails
Although the levels are declining, because of worldwide past uses, most people have some level of PCBs in their blood. Because PCBs are so widespread, do not break down easily in the environment, and can accumulate in people, they have been heavily studied. Fish, other meats, eggs, and milk-based products are the most common sources of PCB exposure. PCBs that are eaten are more easily absorbed by the body than those that are breathed, touched, or accidentally swallowed (e.g., when a child might ingest PCB-contaminated soil) (ATSDR 2000c).
Before decisions are made to restrict consumption of traditional foods—such as fish and snails harvested from the Agana Swamp and River—consideration should be given to benefits that these foods provide. The nutritional benefits of fish and shellfish are well established. Fish are a healthy source of nourishment and include many important vitamins, minerals, proteins and essential fats. Fats present in fish are generally unsaturated, and are better for heart health than saturated fats found in many other foods. Fish also provide rich sources of omega-3 fatty acids, which are associated with lower rates of heart disease (Nobmann 1997).
These benefits should then be compared to the potential risks, if any, from low levels of chemical contaminants present in the foods. As discussed is the following text, ATSDR concludes that eating fish, eels, and snails from the Agana Swamp and River does not pose a public health hazard from chemical contaminants. Therefore, there is no reason to restrict consumption of these foods.
PCBs - Non-Cancer Health Effects from Eating Fish, Eels, and Snails
When evaluating whether one would find non-cancer health effects from what people have eaten, touched, or breathed, researchers generally rely on information from studies of people who have been accidentally exposed. In spite of the thousands of PCB studies conducted since the 1960s, the effects of low-level exposures to PCBs on human health remain inconclusive. Most of the human studies have many limitations that make it difficult to establish a clear association between PCB exposure and adverse health effects (ATSDR 2000c). On the basis of human experience and animal studies, non-cancer health effects of PCBs may include skin effects such as chloracne, hyperpigmentation of the nails and skin, and skin irritation, as well as developmental effects such as abnormal reflexes, motor immaturity, and deficits in memory, learning, and IQ (ATSDR 2000c). Appendix F provides information about the most frequently discussed health concerns from PCB exposure.
In addition to the human studies, it is useful to compare these levels to those commonly found in the food supply. Total Diet Studies (TDS), sometimes called Market Basket Studies, are ongoing programs that determine levels of various pesticide residues, contaminants, and nutrients in foods. For example, the USFDA purchases foods from supermarkets or grocery stores around the U.S., prepares them as they will be eaten, and then analyzes them (FDA 2000). Table 4 shows that the average level of PCBs in the majority of sampled Mongmong fish, eels, and snails is almost identical to or below many common foods eaten daily in the United States and other countries.
Table 4. PCB Residues Detected in Domestic Foods
|
Food item |
Average level detected (mg/kg) |
| Mongmong Catfish Fillet | 0.021 |
| Mongmong Eel Fillet | 0.059 |
| Mongmong Apple Snails | 0.0025 |
| Mongmong Tilapia fillet | 0.14‡ |
| Canada Freshwater fish* | 0.0032 |
| Canada Tuna - canned in oil* | 0.021 |
| Canada Shellfish* | 0.0023 |
| U.S. Beef steak† | 0.022 |
| U.S. Canned tuna† | 0.045 |
| U.S. Pancake mix† | 0.024 |
| U.S. Meatloaf† | 0.023 |
| U.S. Chicken breast† | 0.032 |
| U.S. Salmon steak† | 0.032 |
*Mes J et al 1989
†FDA 2000
‡Not an average
The USFDA has established allowable tolerance levels for PCBs in fish and shellfish at 2.0 mg/kg. All of the samples taken from the Agana Swamp and River were well below this tolerance level for interstate commerce. In addition, most of the exposure doses that ATSDR calculated were at or below ATSDR's health protective minimal risk level (MRL) for PCBs of 0.00002 mg/kg/day (see Appendix E, Table E-2). The highest calculated dose, 0.00013 mg/kg/day from the tilapia, was at least 540 times below the PCB exposure dose range where workers received daily exposures of 0.07- 0.14 mg/kg/day for years with no signs of adverse health effects (Kimbrough 1995). Therefore, ATSDR concludes that the past consumption of fish, eels, and snails from the Agana Swamp and River would not have posed a public health hazard.
ATSDR believes it
is prudent to reduce contaminant levels both in the environment and in what
people consume. When determining reduction levels, ATSDR relies on human studies
if they are available. If human studies are not available, animal studies are
used—they provide specific information about the exact contaminant amounts eaten,
at what frequency, and for how long. For comparisons, ATSDR used information
about eating habits of people in three Guam villages (US Navy 2002), and two
widely referenced animal studies to calculate a target number of fish, eels,
and snail meals people should try to stay within if they eat only from the Agana
Swamp.
The calculations are based on an average meal size of 8.9 ounces, or just over ½ pound, and assume that the people of Mongmong only eat fish, eels, and snails caught in the Agana Swamp and River area. Additional assumptions are listed in Appendix E. Table 5 shows the number of meals for each type of fish.
Table 5: Estimated Number of Fish, Eels, and Snails Meals without Exceeding USEPA's Risk Model Reference Dose
| Fish Type | Adult: meals per month* | Child: meals per month† |
| Tilapia fillet | 1.2 | 0.5 |
| Apple snail | 68.5 | 29.1 |
| Eel fillet | 2.9 | 1.2 |
| Catfish fillet | 8.2 | 3.5 |
* Meal size = 8.9 ounces
†Meal size = 4.5 ounces
Eating more fish meals than listed in Table 5 does not mean a person will experience adverse health effects. It only means that a person's exposure dose would exceed USEPA's health protective reference dose (RfD) of 0.00002 mg/kg/day. Also, the number of meals per month is only a target.
PCBs - Cancer Effects from Eating Fish, Eels, and Snails
ATSDR reviewed many studies examining PCB-exposure levels and cancer in both animals and humans. Studies of human populations do not present strong evidence that PCBs produce cancer in humans. Although some epidemiological studies provide suggestive evidence, these studies have limitations that weaken the association between PCB exposure and cancer in humans. Most human studies have either been inconclusive or have not shown any association between PCBs and human cancer (ATSDR 2000c).
ATSDR's Toxicological Profile for Polychlorinated Biphenyls does not list any Cancer Effect Level for humans (ATSDR 2000c). The human equivalent dose from a study where rats had an increase in tumors corresponded to a 1.52 mg/kg/day exposure dose (Brunner et al. 1996). The highest exposure level to PCBs for adults eating tilapia from the Agana Swamp and River was 0.000077 mg/kg/day—more than 19,000 times lower than the human equivalent to the where cancer was seen in rats.
ATSDR estimated exposure dose and risk estimates for cancer effects from eating fish, eels, and snails with PCBs harvested from Agana Swamp and River for both children and adults. These were calculated using USEPA's cancer slope factor for PCBs and compared to a risk level. The risk level of 0.0001 (1/10,000) was used because it reflects realistic human exposures. Still, risk levels are hypothetical/theoretical. For example, if calculated risk is 1/10,000 then the actual risk is lower and could be as low as 1-in-a billion, 1-in-a trillion or even zero. The slope factor and risk level method are protective by design and none of the risk estimates exceeded the comparison value. These calculations and assumptions are in Appendix E.
PCBs
- Fruits and Vegetables
PCBs cling tightly to organic components in soils and do not dissolve easily in water; thus significant leaching and uptake in plants does not occur (ATSDR 1990). This has proven to be true for the PCB levels found in fruits and vegetables in Agana Swamp. None of the fruits and vegetables sampled had detectable levels of PCBs. ATSDR concludes that eating the fruits and vegetables collected from the areas near or in the Agana Swamp do not present a PCB-related public health hazard.
Total Dioxins - Fish, Eels, and Snails
Total Dioxins - Non-Cancer Health Effects from Eating Fish, Eels, and Snails
The World Health Organization (WHO) has set a tolerable daily intake (TDI) for total dioxins at a range of 1 to 4 x 10-9 mg/kg/day. This range is based on the examination of adverse health effects seen in animal and human studies (WHO 1998). ATSDR has set a protective MRL of 1 x 10-9 mg/kg/day. Studies in Japan, Canada, Germany, Italy, and the Netherlands have estimated daily total dioxin intakes in the general population from 1 to 7 x10-9 mg/kg/day (Masuda 1996). A study of a group of people involved in a mass food poisoning of dioxins, furans, and PCBs over several months in western Japan showed that people consumed, on average, 14 x 10-9 mg/kg/day of total dioxins from contaminated rice oil. The only adverse health effects observed in this group of people was chloracne, a skin disease caused by chlorinated compounds that disappears once exposure stops (Masuda 1996). The ranges of exposure doses from fish, eels and snails from the Agana Swamp and River are from 2.4 x 10-11 to 1.4 x 10-9 mg/kg/day. These values are at least 10 times below those values found in the Japan food poisoning study and well within the WHO's TDI range, ATSDR's MRL, and the ranges found in other countries.
ATSDR reviewed the literature for information about total dioxins in the food supply of the U.S. and other countries. Table 6 presents levels of dioxin residues detected in common foods. The average levels of total dioxins in the majority of sampled Mongmong fish, eels, and snails is almost identical to or below many common foods eaten daily in the United States and other countries.
Table 6. Total Dioxin Residues Detected in Domestic Foods
| Food item | Average level detected (mg/kg) | Average level detected (mg/kg) |
| Mongmong Apple Snail | 3.7 x 10-8 | .000 000 037 |
| Mongmong Tilapia Fillet |
3.4 x 10-7** |
.000 000 34 |
| Mongmong Catfish Fillet | 2.7 x 10-7 | .000 000 27 |
| Mongmong Eel Fillet |
7.6 x 10-7 |
.000 000 76 |
| Spain Seafood* | 4.2 x 10-7 | .000 000 42 |
| Spain Poultry* | 1.1 x 10-7 | .000 000 11 |
| Spain Milk (whole)* | 1.8 x 10-7 | .000 000 18 |
| Former Soviet Union Fish† | 7.0 x 10-8 | .000 000 07 |
| Former Soviet Union Beef† | 1.3 x 10-7 | .000 000 13 |
| Former Soviet Union Pork† | 5.0 x 10-8 | .000 000 05 |
| Former Soviet Union Cream† | 8.0 x 10-7 | .000 000 8 |
| U.S. Ground Beef‡ | 1.5 x 10-6 | .000 001 5 |
| U.S. Haddock Fillet‡ | 2.0 x 10-8 | .000 000 02 |
| U.S. Cooked Ham‡ | 3.0 x 10-7 | .000 000 3 |
| U.S. Pork Chop‡ | 3.0 x 10-7 | .000 000 3 |
| U.S. Chicken‡ | 3.0 x 10-8 | .000 000 03 |
| U.S. Heavy Cream‡ | 4.0 x 10-7 | .000 000 4 |
* Domingo et al 1999
†Schecter et al 1992
‡ Schecter 1993
**Not an average
Table 7 shows ATSDR's estimated total dioxin exposure doses from eating fish, eels, and snails harvested from Agana Swamp and River for non-cancer effects for both children and adults. These values are compared to ATSDR's MRL—a very health-protective risk level. See Appendix E for exposure evaluation methodology and assumptions.
Table 7. Estimated Dioxin Exposure Doses from Eating Fish, Eels and Snails from the Agana Swamp and River
| Type of fish | Adult Dose (mg/kg/day) | Child Dose (mg/kg/day) | MRL (mg/kg/day) |
| Apple snail | 2.4 x 10-11 | 5.6 x 10-11 | 1.0 x 10-9 |
| Tilapia fillet | 5.1 x 10-10 | 1.2 x 10-9 | 1.0 x 10-9 |
| Catfish fillet | 3.3 x 10-10 | 7.8 x 10-10 | 1.0 x 10-9 |
| Eel fillet | 1.4 x 10-9 | 3.2 x 10-9 | 1.0 x 10-9 |
With the exception of the eel fillet, the doses for fish, eels, and snails from the Agana Swamp and River are three times lower than the protective comparisons. Again, exceeding the MRL does not mean that the levels will cause adverse health effects. The dioxin concentrations found in Mongmong fish, eels, and snails were essentially in the same concentration range as found in other meat and dairy products in the United States and other countries. The exposure doses for both adults and children were below or very close to the health-protective MRL. In addition, the doses are equivalent to those found in other countries, within the WHO's TDI range, at least 10 times below levels that were associated with adverse health effects in Japan, and at least 375 times below levels causing adverse health effects in animals (ATSDR 2000c). Therefore, the dioxin levels present in the fish, eels, and snails from Agana Swamp and River do not present a public health hazard.
Total Dioxins - Cancer Effects
ATSDR estimated exposure dose and risk estimates for total dioxins from eating fish, eels, and snails harvested from Agana Swamp and River for cancer effects for adults. These were calculated using USEPA's cancer slope factor for dioxin and compared to a risk level of 0.0001. The slope factor and risk level methods are protective of human health by design. None of the calculations exceeded the risk level. Thus ATSDR concludes that eating fish, eels, and snails from the Agana Swamp and River would not result in an increased dioxin-related cancer risk.
Relatively
low levels of PCBs were found in the soil samples from both the Agana Power
Plant property and in runoff areas. From the data and information reviewed,
it does not appear that large, highly concentrated spills of PCBs or other chemicals
occurred. Rather, the PCB contamination resulted from smaller, less concentrated
spills. Therefore, levels of PCBs in soil were also expected to have been low
in the past. Because of these low levels, adverse health effects from human
exposure to chemical contamination are not expected.
What Was Sampled?
During 1998, 1999 and 2000, surface and subsurface soil sampling for PCBs and other contaminants was performed on the APP property, in the drainage areas, and on residential properties. ATSDR believes that the Navy's sampling identified the areas most likely to be contaminated and provides enough information to make a health determination.
West Drainage Area
In 1998 and 1999, the Navy collected eight surface soil samples from the West Drainage area (Figure 2) including one from the drainage ditch near the Nuestra Senora De Las Aguas Catholic Church. The contaminant levels ranged from not detected to 29 mg/kg (from near the church), with an average value of 3.69 mg/kg (US Navy 1999f).
In February 1999, the Navy removed 3 cubic yards of soil from the vicinity of Nuestra Senora de las Aguas Church (Figure 2), to a depth of 2 feet below grade surface and replaced it with clean fill material (US Navy 1999a; US Navy 1999d). After remediation the PCB contaminant level near the church averaged of 0.53 mg/kg.
Residential Areas
During 1998 and 1999 a total of 38 surface soil samples were collected by the Navy from residential properties adjacent to the southern end APP and southwest of the plant along Roy T. Damian Road. The samples were analyzed for PCBs, which were either not detected or found at very low concentrations with an average value of 0.065 mg/kg. The maximum concentration was 0.55 mg/kg (US Navy 1999f).
Agana Power Plant Property
The Navy sampled soil in seven areas, or Points of Interest (POI), on the Agana Power Plant property. The Navy's fall 1998 soil testing on the plant property indicated that PCBs were present in the soil. Soils with relative higher levels of PCBs were removed to prevent contaminant migration off site (US Navy 1999b). Because people are not likely to accidently ingest soil from this area, ATSDR did not evaluate exposure on the APP property.
Outfall Drainage Area
During 1998 and 1999 a total of 119 surface soil and 57 subsurface soil samples were collected by the Navy from the Outfall Drainage area. The Navy conducted a time-critical removal action (TCRA) in this area during the end of 2000 because of relatively higher levels of PCBs (US Navy 2001). The majority of this remediation was within the Navy's utility right-of-way and included the Tangantan scrub woodland of the Upland Outfall and the heavily vegetated Wetland Outfall. Because people are not likely to accidentally ingest the soil, ATSDR did not evaluate exposure to PCBs in the Outfall Drainage area.
Past Drainage Areas
There have been changes in the drainage patterns from the APP because of the construction of concrete swales. There were concerns from individuals and families that the soil levels in the past might have been higher in areas where the drainage used to go, such as residential properties. Several subsurface soil samples have been taken in the Outfall Drainage area at depths ranging from 1.5 to 6 feet. These samples show that the range of contaminant concentrations in soil below the surface is not very different from those in the surface soil. Therefore the contamination from the APP was not likely to have been higher where the drainage used to go, including residential areas.
Exposure Evaluation and Public Health Implications for Accidentally Ingesting Soil from the West Drainage and Residential Areas
ATSDR evaluated exposure from accidentally ingesting soil for people who garden or children who play in the West Drainage and residential areas. PCBs cling tightly to soil; thus when people come in contact with contaminated soils, PCBs are not easily absorbed by the body. ATSDR performed screening level mathematical calculations, including exposure dose estimates and risk calculations that used a set of worst case assumptions about exposure to determine how likely people are to have adverse health effects. These assumptions overestimated the amount of contaminants people would ingest. Appendix D contains information about how ATSDR assesses exposure, and Appendix E contains assumptions and methodology.
Furthermore, as part of the evaluation of uncertainty, ATSDR considered the fact that PCB levels associated with clay and organic particles could be different at varying depths of soil when analyzed as a single sample (i.e., 0-6 inches). Nevertheless, ATSDR believes that actual PCB exposure and uptake by children and other family memebers would be less than predicted by the calculations included in this report. This is based on (1) protective assumptions in the calculations combined with site specific information and the fate and transport properties of PCBs and (2) comparison of the calculated values with those from other ATSDR evaluations of sites with higher levels of PCBs in soil, including the most recent evaluation of PCB soil contamination on Saipan.
Concentrations of
PCBs along the West Drainage area before and after remediation near the church
have a mean of 3.69 mg/kg and 0.53 mg/kg, respectively. The PCBs in the residential
area south of the APP and adjacent to the Outfall Drainage has a mean 0.065
mg/kg. ATSDR estimated soil exposure doses with these concentrations for 5 different
groups. These included (1) infants aged 6 months to 3 years exhibiting pica
behavior by eating soil, (2) infants aged 6 months to 3 years not exhibiting
pica behavior, (3) young children aged 3 to 12 years old, (4) teenagers aged
12 to 18 years old, and (5) adults (including pregnant women and the elderly
). The amount of soil each age group ingested was overestimated; ATSDR assumed
that 100% of the PCBs were absorbed by the body, although scientific literature
indicates that only 40-65% of PCBs ingested from soil are absorbed (ATSDR 2000c).
For all the non-pica age groups, the estimated exposures to PCBs from soil ingestion ranged from 1 to 8 times below ATSDR's MRL for non-cancer health effects for the West Drainage area before remediation, and from 6 to 54 times below the MRL after remediation. In the residential area, the estimated exposure doses ranged from 47 to 443 times below the MRL. For children exhibiting pica behavior, the estimated exposure was 7 times below the MRL in the residential area and equivalent to the MRL in the West Drainage area after remediation. The estimated exposure for the West Drainage area before remediation near the church was higher than the MRL at 0.0002 mg/kg/day. However, this estimated dose represents an acute, one-time exposure. Based on human and animal studies of acute oral exposure to PCBs, ATSDR does not believe that children exhibiting pica behavior by eating soil would have experienced any health effects.
The estimated cancer risk for adults was calculated using USEPA's cancer slope factor for PCBs and compared to a risk level of 0.0001. The exposure levels calculated for the locations were below the risk level. Therefore, ATSDR concludes that contact resulting in accidental ingestion of soils from these areas does not pose a public health hazard.
Relatively low levels of PCBs have been found in the sediments of the Agana Swamp. Because PCBs do not easily dissolve in water and would have been diluted by the large volume of water in the swamp, contacting the water while swimming and wading, or even accidentally ingesting sediment, likely would not have posed a health hazard from PCBs.
Still, ATSDR's review of information shows that the possible biologic contamination of water in the Agana Swamp could pose a hazard. Swimming or wading with open cuts or wounds could increase the likelihood of an infection, and accidentally ingesting water could result in gastrointestinal problems including diarrhea and abdominal cramps. Eye and throat infections may also occur. Therefore ATSDR recommends further characterization of biologic hazards in the swamp.
What Has Been Sampled?
The Navy collected eight sediment samples from seven locations in the Agana Swamp and River in April 1999 and analyzed them for PCB concentration. The sediment samples range from 0.04 mg/kg to 0.24 mg/kg. Two surface water samples were also collected from this area but had no detections for PCB Aroclors (US Navy 1999f). No historical chemical samples from the swamp prior to the Navy's 1999 sampling are known to have been collected. Water samples of the Guam Water Authority wells near the Agana Springs were all non-detect for PCB contamination (Guam Water Authority 1996).
Exposure Evaluation and Public Health Implications for Swimming and Wading in the Agana Swamp and River
The low chemical levels in the Agana Swamp and River are not a problem for swimming and wading, but a hazard could be associated with bacteria.
A. Community Health Issues
During ATSDR's community meetings, people wanted more information on the following health issues and whether they were related to PCB exposures from the Agana Power Plant.
ATSDR's evaluation showed that none of these health concerns were related to PCB exposure. Information on the known associations for these health issues and other information is provided in Appendix G.
B. Community Questions on the Agana Swamp and River
Is there a need for a fish consumption advisory because of PCBs?
No. PCBs and other chemicals have been found in the fish, eels, and snails in the Agana Swamp. In May 2000, GDPHSS placed a temporary fishing ban in Agana Swamp until additional sampling—taking into account seasonal variations—could provide better information to assess the risks associated with eating the fish. ATSDR evaluated the new data and found that chemical exposure did not pose a hazard. Bacterial contamination, however, could still present a health hazard.
Was it safe and is it now safe to eat aquatic (apple) snails?
People should only eat aquatic snails that have been thoroughly cooked. The Marine Laboratory at the University of Guam detected parasites in aquatic snails; eating them uncooked can result in meningoencephalitis. But according to GDPHSS, in the last 20 years no cases of have been traced back to people eating snails or other foods from the swamp.
Was it safe from the 1950s to the present to eat fish, eels, and snails caught in the swamp, from bridges in the Agana River, or from other drainage outfall areas in the bay?
Yes. The PCB levels measured in the fish, eels, and snails from Agana Swamp and River were too low to cause any adverse health effects. Even if PCB levels were higher in the past, they would probably have been too low to be of concern.
Was it safe from the 1950s to the present to eat fruits and vegetables grown in and around the Agana Swamp?
Yes. The fruits and vegetables around the Agana Swamp and River did not have detectable levels of PCBs. Fruits and vegetables grown in the same locations in the past were just as safe to eat because PCBs cling tightly to organic components in the soil and are not easily taken up by plants.
It is unlikely that the vegetation was a significant source of PCBs since plants do not readily accumulate organic chemicals into their root systems. PCBs can be deposited onto the surface of vegetation and ingested. Levels of PCBs were relatively low in the soils. Washing fruit and vegetables would have helped remove PCB deposited on the surface of the fruits and vegetables. The Navy did not collect any samples of commonly consumed fruit and/or vegetables in locations where PCBs were detected in soil near the APP Drainage Outfall. PCB levels in the soils at these locations have been removed. PCBs in surface water samples collected by the Navy were only detected in a few samples at very low concentrations (US Navy 2003).
There was a large fish kill in the 1960s below the bridge. Was it related to PCBs?
We will possibly never know the cause of the fish kill in the swamp during the 1960s as there are many causes of fish kills including low oxygen levels, water temperature variations, infections, etc. However, a release of PCBs would not typically cause a one-time short-term fish kill event.
I want to make a fish farm in one area of the swamp. Is it safe to raise fish for sale here? I want to grow fruits and vegetables in the swamp and sell them. Would this be safe?
There are many possible sources of pollution (both chemical and biological) in and around the Mongmong area. As many outfalls and areas of the Agana Swamp have not been fully sampled, people wanting to set up an animal (e.g., fish, chickens, etc.) or plant (i.e., fruit, vegetable) farm should contact GEPA and review of the documents on known contamination areas before they begin farming. All stakeholders (US Navy, US Army Corps of Engineers, UOG, US Fish and Wildlife Service, USGS, Guam Department of Agriculture) should provide GEPA with all relevant data collected in hardcopy and electronic format including GIS coordinates. ATSDR recommends that a management plan (including maps, preferably in GIS format) be developed so that people can make informed choices before setting up operations such as farms. For additional information on setting up farms, people should contact the Guam Department of Agriculture.
C. Community Questions on Contact with Contaminated Soils
Would playing in yards near APP or at the old elementary school have been harmful to our children's health?
No. PCBs cling tightly to soil, so when people come in contact with contaminated soils PCBs are not easily absorbed by the body. Contact with contaminated soils is unlikely to be an important contributor to to an individual's total body burden of PCBs. In fact, studies of people living in the areas of PCB-contaminated soil have not demonstrated adverse health effects that could be attributed to PCBs (ATSDR 2000c). Therefore, playing in yards near the APP or at the elementary school was not harmful to children's health.
Is it now safe for our children to play in the ditches where runoff water collects from APP?
Runoff from the Agana Power Plant is unlikely to contain contamination. The Navy has characterized and remediated contaminated areas at the Plant.
PCBs likely soaked deeper in the soil than the sample depths. Why didn't the Navy sample deeper?
The Navy sampled in areas where people might come in contact with the soil. If there are PCBs deeper than the Navy sampled—which was 3 to 6 feet in some areas—the chance that people will be over exposed to that soil is unlikely.
The drainage flow has changed here over the years. There was not a retaining wall around APP either. How do we know that the right areas were sampled and the whole area is not contaminated?
Initial sampling was based on known locations of PCB-containing equipment, visible soil staining, the direction of runoff flow, and interviews with previous APP workers. The Navy has taken many soil samples both at and below the surface. These samples show that the levels of PCBs in the soil below the surface are not very different from the levels of PCBs on the surface. This indicates that the change in drainage flow did not leave areas of high contamination. Therefore, areas within the old drainage flow area did not likely have higher contamination than those areas within the current drainage pathways. Because the concentration of PCBs was similar in surface and subsurface soils it is less likely that the relatively low levels of PCBs were on average more concentrated in more organic and clay material at the very top of the surface soil sample. For these reasons ATSDR believes that the sampling is representative and has identified areas of PCB contamination from the former APP.
What if I was exposed from both the foods and the soils? Would my exposure dose be more?
ATSDR considered that some people could be exposed to chemical contaminants from consuming foods from the Agana Swamp and River and accidentally ingesting soil while gardening or playing in the drainage ditch. The estimated total dose levels of all combined exposures to PCBs and other contaminants were, however, low and would not likely result in adverse health effects—even to sensitive groups such as children.
D. Community Questions on Swimming and Wading in the Agana Swamp and River
Was it safe from the 1950s to the present to swim or wade in the Agana Swamp?
Exposure to PCBs via swimming or wading in the Agana Swamp now and in the past would not have posed a public health hazard. Still, there is a history of bacterial contamination in the swamp that could have caused adverse health effects in the past and could cause them now. Swimming or wading with open cuts or wounds could increase the likelihood of an infection; accidentally ingesting the water could result in gastrointestinal problems. ATSDR recommends further characterization of this and other hazards in the swamp.
Could occasionally swallowing the water also make me sick?
Occasionally swallowing the water would not have posed a health hazard from PCBs because both the PCB concentrations and ingestion frequency would have been low. However, bacterial contamination in the swamp could cause illness.
V. ATSDR's CHILD HEALTH CONCERNS
ATSDR is committed to protecting children's health in Mongmong. ATSDR recognizes that infants and children might be more vulnerable than adults to environmental exposure. This vulnerability results from several factors, including (1) children are smaller than adults, resulting in higher doses of chemical exposure per unit body weight, (2) children are more likely to play outdoors and bring food into contaminated areas and, as a result, can contact and ingest soil particles at higher rates than adults, and (3) children's bodies can be more sensitive to the effects of chemical exposures. Children have developing body systems which can sustain permanent damage if toxic exposures occur during critical growth stages. Because of these sensitivities, ATSDR uses health guidelines that are protective for children.
Conclusions about Child Health in Areas Affected by PCBs from the Agana Power Plant
ATSDR evaluated the exposures children would experience from foods eaten from the Agana Swamp, playing in areas with contaminated soils, and swimming or wading in the Agana Swamp. Although children were exposed to chemical contaminants, ATSDR would not expect to see adverse health effects from the exposures. Although no certainty exists regarding biologic contamination, it is suspected. ATSDR is recommending measures to reduce the likelihood of illness from biologic exposures.
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